For a large number of seal uses, it has proven to be beneficial to employ a unitized seal wherein a seal is combined with a wear sleeve in a single unitized assembly. The incorporation of a good wear surface into a seal assembly to form a unitized unit has resulted in both increased seal life and shaft life for many shaft seal applications and is even more important with the development of lined seals to protect the seal lip to wear sleeve interface from damage prior to installation, during installation and during removal. This allows the design and choice of materials to be selected for best application performance without the need to consider possible disassembly damage. This has led to the development of a substantial number of unitized seal constructions.
Some prior art unitized seals incorporate a unitized structure wherein the wear sleeve members are formed from a plurality of nested parts which are locked together. These seal units have tended to leak in the area between the nested metal members and have often required the use of additional gasket material to reduce such leakage. Attempts have been made to design more reliable unitized seals having wear sleeves formed from nested parts which do not require additional gasket material as illustrated by U.S. Pat. Nos. 3,275,333 to A.M. Scott et al and 3,479,728 to P.C. Burfield et al. These seal designs do effectively reduce the expense previously incurred in providing gaskets between the wear sleeve sections of a multi-part unitized seal, but such seals still require additional expense for the formation of the plurality of seal parts used in the assembly. These parts must be individually stamped or molded, and often three or more stamped components and a plurality of molding operations are necessitated for the formation of a single unitized seal.
With many known unitized seals, the seal structure is such that the seal is easily damaged during assembly or disassembly. Often the unitizing joint for the seal is located in close proximity to the elastomeric seal lip, thereby exposing the seal lip to possible damage by contact with the seal unitizing joint during seal assembly or disassembly. U.S. Pat. No. 3,022,081 to T.O. Kostaka illustrates a unitized seal which may be easily disassembled by deflecting the rubber seal element. However, in some instances, the seal element might become exposed to sharp metal edges of metal seal components during this disassembly operation, and damage to the seal contact surface is thereby possible, and in the case of lined seals, likely. Consequently, a need has arisen for the development of a simple, inexpensive unitized seal structure designed to reduce the possibility of damage to a sealing lip during either assembly, disassembly or installation of the seal.